Websocket

Introduction

In this post, I will show you how to integrate kafka consumer with websocket server. The websocket server will send message to client when it receives message from kafka consumer. source code

Start kafka server and install heizer
Create a kafka topic topic.test. (you can create new topic in kafka-ui)

Create websocket server server.py on ws://localhost:8001. code

import asyncio

import websockets

from heizer import ConsumerConfig, Message, Topic, consumer

consumer_config = ConsumerConfig(
    bootstrap_servers="localhost:9092",
    group_id="websockets_sample",
    auto_offset_reset="earliest",
    enable_auto_commit=False,
)

topics = [Topic(name="my.topic1")]


@consumer(topics=topics, config=consumer_config, is_async=True, init_topics=True, name="websocket_sample")
async def handler(message: Message, C: consumer, websocket, *args, **kwargs):
    print(C.name)
    await websocket.send(message.value)


async def main():
    async with websockets.serve(handler, "", 8001):
        try:
            await asyncio.Future()
        except KeyboardInterrupt:
            return


if __name__ == "__main__":
    asyncio.run(main())

python server.py

Create websocket client client.html and listen to ws://localhost:8001. html file

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <meta http-equiv="X-UA-Compatible" content="IE=edge">

    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <title>WebSocker Client</title>

</head>

<body>

<div id="msgs"></div>

</body>

<script>
    var msgs = [];

    const socket = new WebSocket('ws://localhost:8001');

    socket.addEventListener('open', function (event) {

        socket.send('Connection Established');

    });

    const msg_box = document.getElementById("msgs");

    socket.addEventListener('message', function (event) {
        msgs.push(event.data);
        console.log(event.data);

        msg_box.innerHTML = msgs.join("<br>");

    });

</script>

</html>

and open client.html in browser

Publish message to kafka topic topic.test and you will see the message in browser
You will see the message in browser